The subcutaneous accumulation of fat is correlated with the impaired function of fat cells; fat cells contain fats in the forms of free fatty acid and triglyceride. Triglyceride, which has been formed and accumulated in the fat cells, is also again decomposed to fatty acid, glycerol, and/or glycerol ester by enzymatic degradation. However, when significant imbalance between fat formation and fat decomposition occurs in the body due to various reasons (e.g. poor hormonal function, too abundant diet, inactivation, and aging), triglyceride accumulates in fat cells, resulting in subcutaneous accumulation of fat. Consequently, overweight and therapeutic/cosmetic problems arise.
A method, where a composition which removes the subcutaneous accumulation of fat is directly injected under the skin, has been applied to the treatment of subcutaneous fat accumulation or an obesity accompanied by an excessive fat layer. A phosphatidylcholine preparation represented by Lipostabil (Sanofi-Aventis) is used for that purpose (Patent Literatures 2 and 3). However, the method has raised questions about safety as well as pain during operation, and the method can be said to be a high-risk method. In addition, in the production process of the preparation used for the method, phosphatidylcholine is dissolved together with a solubilizer (bile acid) in an organic solvent, and after concentration and drying, it is dispersed in water to provide a liposome under high pressure. Thus, the process requires a complex and advanced technology as well as great expense. Further, the transdermal administration of the composition also requires a physical auxiliary operation such as iontophoresis.
On the other hand, phosphatidylcholine is widely used as an emulsifier for medicinal products or cosmetics. However, temporal stability is also an important issue in that case (Patent Literature 1).
In addition, there has been growing demand for weight loss from the viewpoint of beauty as well as obesity accompanied by an excessive fat layer, and phosphatidylcholine derivative is also used for that purpose. However, a preparation for transdermal administration of phosphatidylcholine which allows self-administration, has not been found.